Lines in ggplot with segment function

Question

I have the following script from the DTW package and I'm looking for the equivalent code of this example in ggplot framework:

library(dtw)
idx<-seq(0,6.28,len=100);
query<-sin(idx)+runif(100)/10;
reference<-cos(idx)

plot(reference); 
lines(query,col="blue");
alignment<-dtw(query,reference);


#how can I add line on the ggplot plot ?  with geom_segment ?
plot(reference)
lines(query[alignment$index1]~alignment$index2,col="blue")

and how to interpret the symbol tilde in this use case in the lines function ?

Can you add the result to your question?

Tung
– Tung

2018-10-23 11:00:00 +00:00
Commented Oct 23, 2018 at 11:00 — Tung
– Tung, Commented Oct 23, 2018 at 11:00

TheRimalaya · Accepted Answer · 2018-10-23 20:39:34Z

1

Take a look at it, hope this will help,

df <- tibble(
  row_num = 1:100,
  idx = seq(0, 6.28, len = 100),
  query = sin(idx) + runif(100)/10,
  reference = cos(idx)
)
alignment <- with(df, dtw(query, reference))
seg_df <- tibble(
  x = alignment$index2,
  y = df$query[alignment$index1]
)
ggplot(df, aes(row_num, reference)) +
  geom_point(shape = 21) +
  geom_path(data = seg_df, aes(x = x, y = y, col = "blue"))

EDIT: for different query and reference

You can always create different data frame for query and reference as,

library(tibble)
library(ggplot2)
library(dtw)

query <- tibble(
  row_num = 1:100,
  idx = seq(0, 6.28, len = 100),
  query = sin(idx) + runif(100)/10
)
ref <- tibble(
  row_num = 1:50,
  idx = seq(0, 6.28, len = 50),
  reference = cos(idx)
)
alignment <- dtw(query$query, ref$reference)
seg_df <- tibble(
  x = alignment$index2,
  y = query$query[alignment$index1]
)
plt <- ggplot(ref, aes(row_num, reference)) +
  geom_point(shape = 21) +
  geom_path(data = seg_df, aes(x = x, y = y), col = "blue")
plot(plt)

edited Oct 23, 2018 at 20:39

answered Oct 23, 2018 at 11:15

TheRimalaya

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1 Comment

ZchGarinch Over a year ago

thank you, it works fine for the equal length sequence (query and reference have here length of 100) but but what about the seqences that are not the same length ?

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